35 years later, Keller discovers a somewhat more general quantization, but he assumes at first (in contrast to Einstein) its universal applicability. Fritz Reiche, the successor at Einstein's chair (after his emigration) at the Berlin University calls Keller's attention to the 1917 paper, and the latter draws it from oblivion.

Further twenty years later physics recalls Poincaré as well who had discovered, already around 1900, the chaotic behaviour of planetary orbits.